Many electronic devices are powered by batteries. Rechargeable batteries are often used to avoid the cost of replacing conventional dry-cell batteries and to conserve precious resources. However, recharging batteries with conventional rechargeable battery chargers requires access to an alternating current (AC) power outlet, which is sometimes not available or not convenient. It would, therefore, be desirable to derive power for electronics wirelessly.
In the field of wireless charging, safe and reliable use within a business or home environment is of the utmost concern. To date, wireless charging has been limited to magnetic or inductive charging based solutions. Unfortunately, these solutions require a wireless power transmission system and a receiver to be in relatively close proximity to one another. Wireless power transmission at larger distances requires more advanced mechanisms such as, for example, transmission via radio frequency (RF) signals, ultrasonic transmissions, laser powering, to name a few, each of which presents a number of unique hurdles to commercial success.
The most viable systems to date utilize power transmission via RF. However, in the context of RF transmission within a residence, commercial building, or other habited environment, there are many reasons to limit the RF exposure levels of the transmitted signals. Consequently, power delivery is constrained to relatively low power levels (typically on the order of milliWatts). Due to this low energy transfer rate, it is imperative that the system is efficient.
In a free space wireless environment, radiation from an omnidirectional radiator or antenna propagates as an expanding sphere. The power density is reduced as the surface area of the sphere increases in the ratio of 1/r2 where r is the radius of the sphere. This type of radiator is often referred to as isotropic, with an omnidirectional radiation pattern, and it is usual to refer to antennas in terms of their directivity vs. gain as dBi—decibels over isotropic. If the intended receiver of the transmission is at a particular point relative to the transmitting radiator, being able to direct the power towards an intended receiver means that more power will be available at the receiving system for a given distance than would have been the case if the power had been omnidirectional radiated. This concept of directivity is very important because it improves the system performance. A very simple analog is seen in the use of a small lamp to provide light and the effect of directing the energy using a reflector or lens to make a flashlight where the power is used to illuminate a preferred region at the expense of having little to no illumination elsewhere.
Central to mechanisms for directionally focusing transmissions is the ability to rapidly and efficiently determine transmission phase, and alter outgoing transmission phase. Phase detection is likewise useful for activities such as detecting changes in a charging environment, such as detection of movement of an antenna within the environment. Movement detection allows for more efficient beaconing, and power transmission scheduling.
Accordingly, a need exists for technology that overcomes the problem demonstrated above, as well as one that provides additional benefits. The examples provided herein of some prior or related systems and their associated limitations are intended to be illustrative and not exclusive. Other limitations of existing or prior systems will become apparent to those of skill in the art upon reading the following Detailed Description.
Overview
Examples discussed herein relate to a phase detection systems and methods for rapid phase determination of incoming signals. In some embodiments, the phase detection system includes a phase detection apparatus and a control system. The phase detection apparatus includes a phase shifting element and a phase detector element. The phase shifting element is configured to phase-shift a reference signal multiple times per detection cycle. The phase detector element is configured to compare an incoming signal to multiple phases of the phase-shifted reference signal during the detection cycle, and generate an output indicating a relative phase difference between the incoming signal and the phase-shifted reference signal for each of the multiple phases. The control system is configured to determine a relative phase of the incoming signal based, at least in part, on the outputs.
In some embodiments, a method for rapid phase determination of incoming signals is described. The method includes generating a reference signals at three or more phases wherein the phases are known, detecting a beacon signal, adjusting the amplitudes of the reference signals and the beacon signal until the amplitudes are roughly aligned, comparing each of the three reference signals phases to the beacon signal to generate direct current outputs to a digital controller, and calculating the beacon signal's phase using the known phases and corresponding direct current outputs.
This Overview is provided to introduce a selection of concepts in a simplified form that are further described below in the Technical Disclosure. It may be understood that this Overview is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.